This invention relates to a two cycle engine for a small boat and more particularly to an improved lubricating system for the two cycle engine of a small boat.
As is well known, a wide variety of watercraft are provided with internal combustion engines for powering the watercraft. In connection with the use of an internal combustion engine, it is also the practice to provide a lubricating system for the engine. With two cycle engines, although it has been the practice to mix lubricant with the fuel for the engine, there are a number of advantages to employing a separate lubricating system wherein lubricant is supplied to the engine from a separate lubricant reservoir. In many of these types of lubricating systems, the lubricant reservoir is positioned vertically above the lubricant pump when the watercraft is operating in its normal upright condition so that lubricant will be supplied to the pump under the influence of gravity. With many types of watercraft, particularly those having a highly sporting nature such as some small jet propelled watercraft that are designed to be operated by a rider wearing a swimming suit, it is anticipated that the watercraft will become inverted during its operation.
When the engine is provided with a lubricating system of the type having the lubricant reservoir positioned above the lubricant pump, the inversion of the watercraft can cause air to flow from the reservoir to the pumping system. When this occurs and the watercraft is righted, if the engine is restarted immediately, the lubricant pump will pump air rather than lubricant to the engine. Obvious problems can occur when this happens.
There have been proposed lubricant pumping systems wherein the lubricant pump is provided with a self purging device that will purge air from the lubricant and return it back to the lubricant reservoir through an air return line. With such systems, inversion of the watercraft can also give rise to problems. That is, the return line can become filled with air and when the watercraft is inverted, lubricant can become forced in the line along with the air. When the watercraft is righted, the lubricant in the return line can actually force air back into the lubricant pump and the aforenoted problems will again be possible.
The aforenoted co-pending application discloses several embodiments of arrangements for insuring that in entrained air will not be mixed with the lubricant once the watercraft is righted, even when using an air return line. In the embodiments disclosed in the aforenoted application, this is done by incorporating some form of flow control device in the return line such as a trap or the like. However, even employing such devices can, in some instances, not completely preclude the possibility of air from the return line being forced back into the pump by lubricant which flows into the return line when inverted.
It is, therefore, a principal object of this invention to provide an improved lubricating system for the internal combustion engine of a small watercraft wherein it will be insured that inversion and righting of the watercraft will not cause the lubricant system to deliver air to the engine rather than lubricant.
It is a further object of this invention to provide a lubricating system for a small watercraft of the type having the lubricant reservoir above the lubricant pump and incorporating an arrangement for insuring that air cannot be delivered to the lubricant pump when the watercraft is inverted and then righted.
It is a further object of this invention to provide an arrangement for purging the air from a lubricating system of a small watercraft and wherein the air purging return line will not cause air to be forced back into the lubricant pump if the watercraft is inverted and then righted.
In the aforenoted co-pending application the air return line is provided in the lubricant pump and is intended to deliver air entrained in the lubricant back to the lubricant reservoir at a point above the level of the lubricant therein. In the system shown in the co-pending application, the air return line communicates with the internal portions of the pump at a location between the area where lubricant is delivered to the pump and the lubricant discharge. Because of this intermediate location, there is some possibility that the flow of lubricant through the pump may create a venturi action which could draw air back into the pump during its operation from the air return line.
It is a further object of this invention to provide an improved lubricant pump for a small watercraft.
It is, therefore, a still further object of this invention to provide an improved arrangement for purging air from a lubricant pump without the possibility that the air can be drawn into the pump during its operation.